A developer has to hold a cogent mental model of the problem they’re working on. Someone copying text might be able to do it while thinking of other things. If a developer is interrupted, their mental model “pops” like a bubble, and they might have to mentally start from scratch once they’ve dealt with the interruption.
also, what does original work mean? If you mean in the sense of PhD level research, I haven't worked in a lot of places where 'original work' was done. it is mostly glueing together other people's work (which is original to the person doing the glueing maybe).